Process for preparing a sulphur cement product

ABSTRACT

A process for the preparation of a sulphur cement product is disclosed. Sulphur is mixed with a coupling agent and with a particulate inorganic material at a temperature at which sulphur is molten to obtain a molten sulphur cement product, which is solidified. The coupling agent is supplied as a solid composition comprising the coupling agent and at least 10 wt %, based upon the weight of the solid composition, of carrier material selected from one or more of wax, inorganic filler and polymer. The coupling agent is chosen from the group of organosilanes and organotitanates.

FIELD OF THE INVENTION

The present invention provides a process for the preparation of asulphur cement product; a process for preparing a solid composition foruse in the process for preparing the sulphur cement product; and to asolid composition.

BACKGROUND OF THE INVENTION

Sulphur cement generally refers to a product comprising at least sulphurand a filler. To improve the properties of the sulphur cement, thesulphur may be modified using a sulphur modifier, e.g. naphthalene orolefinic compounds such as 5 ethylidene-2-norbornene (ENB) or 5vinyl-2-norbornene (VNB), dicyclopentadiene, limonene or styrene.Typical sulphur cement fillers are particulate inorganic materials.

Sulphur cement-aggregate composites generally refer to a compositecomprising both sulphur cement and aggregate. Examples of sulphurcement-aggregate composites are sulphur mortar, sulphur concrete andsulphur-extended asphalt.

It is known to use organosilane compounds as a stabilising agent insulphur cement or sulphur cement-aggregate compositions to improve waterstability. In WO 2007/65920, sulphur cement or a sulphurcement-aggregate composite is prepared by admixing an inorganic fillerand a polysulphide-containing organosilane, mixing with molten sulphurand solidifying the admixture.

It is desirable to incorporate the organosilane into the sulphur priorto its use in the sulphur cement manufacturing plant, thereby avoidingthe need for additional and potentially complex process steps at themanufacturing plant. Organosilanes are typically liquid reagents and itis preferable to use solid reagents in the manufacturing plant. WO2008/148804 discloses a process wherein the organosilane is incorporatedinto a sulphur cement pre-composition. The sulphur cementpre-composition can be mixed with particulate inorganic material andoptionally with additional sulphur to provide a sulphur cement product.

The present inventors have however found that the sulphurpre-composition of WO 2008/148804 may be liable to degradation if storedfor an extended period, particularly if the weight percentage oforganosilane is high. Additionally, the organosilanes and molten sulphurcan exhibit poor miscibility, which may lead to phase separations whenpreparing sulphur cement products. The present inventors have thereforesought to provide a method for preparing sulphur cement products whichdoes not suffer from the disadvantages of the prior art, in particular apre-composition that may be stored and does not phase separate whenpreparing sulphur cement products.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a process for thepreparation of a sulphur cement product comprising the steps of:

-   (a) mixing sulphur with a coupling agent and with a particulate    inorganic material at a temperature at which sulphur is molten to    obtain a molten sulphur cement product; and-   (b) solidifying the molten sulphur cement product; wherein the    coupling agent is chosen from the group of organosilanes and    organotitanates, and wherein the coupling agent is supplied as a    solid composition comprising the coupling agent and at least 10 wt    %, based upon the weight of the solid composition, of carrier    material selected from one or more of wax, inorganic filler and    polymer.

The inventors have found that providing the coupling agent in the formof a solid composition comprising the coupling agent and carriermaterial, ensures a simple and effective process. The solid compositioncomprising the coupling agent is stable and can be stored for extendedperiods. The sulphur cement product is not adversely affected by thepresence of the carrier agent in the product.

According to one embodiment of the invention, the present inventionfurther provides a solid composition particularly suitable for use inthe process of the present invention. The solid composition according tothis embodiment of the invention comprises from 20 to 70wt % of acoupling agent chosen from the group of organosilanes andorganotitanates, from 20 to 60 wt % of wax or polymer, and from 10 to 50wt % of inorganic filler, wherein the weight percentages are based uponthe weight of the solid composition.

Solid compositions comprising coupling agents and a carrier materialhave previously been disclosed, e.g. in U.S. Pat. No. 5,766,323.However, the present inventors have devised a process wherein suchcompositions are advantageously used to prepare a sulphur cementproduct. Furthermore the present inventors have devised solidcompositions, different to those previously disclosed, that areparticularly suitable for use in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference herein to a sulphur cement product is to a sulphur cement or asulphur cement-aggregate composite. A sulphur cement refers to acomposition comprising sulphur or modified sulphur and a filler. Sulphurcement fillers are particulate inorganic materials with an averageparticle size of less than 0.1 mm. The filler content of sulphur cementmay vary widely, but is preferably in the range of from 1 to 50 wt %,based on the total weight of the sulphur cement.

Sulphur cement-aggregate composites refer to a composite comprising bothsulphur cement and a particulate inorganic material aggregate. Examplesof sulphur cement-aggregate composites are sulphur mortar, sulphurconcrete and sulphur-extended asphalt. Mortar comprises fine aggregate,typically with particles having an average diameter between 0.1 and 5mm, for example sand, and does not comprise coarse aggregate. Concretecomprises coarse aggregate, typically with particles having an averagediameter between 5 and 40 mm, and optionally comprises fine aggregate.Sulphur-extended asphalt comprises aggregate and a binder that containsfiller and a residual hydrocarbon fraction (usually bitumen), whereinpart of the binder has been replaced by sulphur, usually modifiedsulphur.

The sulphur that is mixed with the coupling agent and the particulateinorganic material is preferably supplied as elemental sulphur ormodified sulphur (wherein elemental sulphur has been modified byinclusion of sulphur modifier, e.g. naphthalene or olefinic compoundssuch as 5 ethylidene-2-norbornene (ENB) or 5 vinyl-2-norbornene (VNB),dicyclopentadiene, limonene or styrene, incorporated in an amount from0.1 to 10 wt % based on the weight of sulphur).

The sulphur is preferably supplied in the form of sulphur pellets. Forthe purpose of this specification, reference herein to “pellets” is toany type of regularly sized particle, including for example flakes,slates or sphere-shaped units such as prills, granules, nuggets andpastilles or half pea sized units.

The particulate inorganic material that is mixed with the coupling agentand the sulphur preferably has oxide or hydroxyl groups on its surface.Examples of suitable particulate inorganic materials are silica, flyash, limestone, quartz, iron oxide, alumina, titania, carbon black,gypsum, talc or mica, sand, gravel, rock or metal-silicates. Such metalsilicates are for example formed upon heating heavy metal containingsludge in order to immobilise the metals. More preferably theparticulate inorganic material is a silica or a silicate. Examples ofsuch silica or silicates are quartz, sand and metal-silicates (e.g.mica).

The particulate inorganic material may consist essentially of a fillermaterial (with an average particle size of less than 0.1 mm) such thatthe sulphur cement product is a sulphur cement. The particulateinorganic material may comprise both filler and fine aggregate (withparticles having an average diameter between 0.1 and 5 mm) such that thesulphur cement product is a sulphur mortar. The particulate inorganicmaterial may comprise filler, coarse aggregate (with particles having anaverage diameter between 5 and 40 mm) and optionally fine aggregate(with particles having an average diameter between 0.1 and 5 mm) suchthat the sulphur cement product is a sulphur concrete.

The coupling agent is chosen from the group of organosilanes andorganotitanates and is preferably an organosilane. The coupling agentmay be a blend of two or more different coupling agents, e.g. anorganosilane and an organotitanate, or two different organosilanes.Organosilanes are compounds having at least one carbon-silicon bond orat least one carbon-oxygen-silicon group, and organotitanates arecompounds having at least one carbon-titanium bond or at least onecarbon-oxygen-titanium group.

Preferred organosilanes are organosilanes of the general molecularformula (I):

(P¹)₃Si-A-Si(P²)₃   (I)

Wherein P¹ and P² are independently alkoxy, acyloxy, aryloxy, alkyl,aryl and halogen and A is a divalent functional group comprising one ormore groups chosen from thiol, sulphide, amine or alkenyl groups.

More preferred organosilanes are organosilanes of the general molecularformula (II):

(R¹O)₃Si-A-Si(OR²)₃   (II)

wherein R¹ and R² are independently C₁₋₆ alkyl and A is a divalentfunctional group comprising one or more groups chosen from thiol,sulphide, amine or alkenyl groups. Preferably R¹ and R² are ethyl ormethyl groups. Preferably A is a polysulphide group of formula—(CH₂)_(x)—S_(y)—(CH₂)_(z)— wherein x is an integer from 1 to 4, y is aninteger from 2 to 8, and z is an integer from 1 to 4. Most preferably xand z are the same and y is from 2 to 6. Particularly preferredorganosilanes are bis(3-triethoxysilylpropyl)tetrasulphide andbis(3-triethoxysilylpropyl)disulphide.

The organosilane is alternatively of general formula (III):

(P³)₃Si-A′  (III)

Wherein P¹ and P² are independently alkoxy, acyloxy, acyloxy, alkyl,aryl and halogen and A′ is an univalent functional group comprising oneor more groups chosen from thiol, sulphide, amine or alkenyl groups.

According to another embodiment, the organosilane is preferably ofgeneral formula (IV):

(R³O)₃Si-A′  (IV)

wherein R³ is C₁₋₆ alkyl and A′ is a univalent functional groupcomprising one or more groups chosen from thiol, sulphide, amine oralkenyl groups. Preferably R³ is an ethyl or methyl group. Preferably,A′ is a thiol group or sulphide group, having the formula—(CH₂)_(p)—S_(q)—(CH₂)_(r)—H, wherein p is an integer from 1 to 4, q isan integer from 1 to 8 and r is 0 or an integer from 1 to 4. In oneembodiment, q is 1 and r is 0, such that A′ is a thiol group. In anotherembodiment, q is from 2 to 8 and r is from 1 to 4, such that A′ is apolysulphide group. In another preferred embodiment, A′ is a primaryamine group of formula —(CH₂)_(n)—NH₂, wherein n is an integer from 1 to4. In yet another preferred embodiment, A′ is an alkenyl group offormula —(CH₂)_(m)—X, wherein m is an integer from 0 to 4 and X is analkenyl group. Possible X groups are shown below:

Preferred organotitanates are of general formula (V) or (VI):

wherein OR⁴, OR⁵ and OR⁶ are independently chosen from acyloxy,phosphato, pyrophosphato, sulfonato and glycoxy; and ZO and Z′O areindependently chosen from alkoxy or neoalkoxy group or ZO and Z′Otogether form a glycoxy group. The OR⁴, OR⁵ and OR⁶ groups arepreferably acyloxy, dialkyl phosphato, dialkyl pyrophosphato oralkylbenzene sulfonato groups. If ZO and/or Z′O are alkoxy groups, Zand/or Z′ are preferably C₁-C₂₅ alkyl. Z and Z′ are most preferablyisopropyl. Organotitanates with neoalkoxy groups are described furtherin U.S. Pat. No. 4,623,738.

Alternatively the organotitanates may be as described in WO 2008/152054.

Step (a) is carried out at a temperature at which sulphur is molten,i.e. typically above 120° C., preferably in the range of from 120 to150° C., more preferably in the range of from 125 to 140° C.

Optionally further ingredients such as sulphur modifiers may be admixedduring step (a). Sulphur modifiers may be added in an amount in therange of from 0.1 to 10 wt % based on the weight of sulphur. Suchmodifiers are known in the art. Examples of such modifiers are aliphaticor aromatic polysulphides or compounds that form polysulphides uponreaction with sulphur. Examples of compounds that form polysulphides arenaphthalene or olefinic compounds such as 5 ethylidene-2-norbornene(BNB) or 5 vinyl-2-norbornene (VNB), dicyclopentadiene, limonene orstyrene.

In step (b) the molten sulphur cement product is solidified by coolingthe product to a temperature at which the sulphur solidifies.

The coupling agent is supplied to step (a) as a solid compositioncomprising the coupling agent and at least 10 wt %, based upon theweight of the solid composition, of carrier material selected from oneor more of wax, inorganic filler and polymer.

According to a preferred embodiment, the solid composition comprises waxas carrier material and the coupling agent is prepared by

-   (a) providing an aqueous solution of an oligosulphide by reacting a    compound of formula (VII):

M_(m)S_(n)   (VII)

wherein M is a nitrogen-containing cation, a phosphorus-containingcation or a metal atom, m is 1 or 2 and n is from 1 to 8, or M ishydrogen, m is 2 and n is 1 with molten sulphur;

-   (b) providing a compound of formula (VIII):

wherein R¹, R² and R³ are independently chosen from alkoxy, acyloxy,aryloxy, alkyl, aryl and halogen, preferably C1-C6 alkoxy, wherein R⁴ isalkylene and wherein X is a leaving group chosen from the groupconsisting of halogen, carboxylate, nitro, azide, thiocyanate, ammonium,phosphonium and sulfonate dissolved in a molten hydrophobic wax;

-   (c) reacting the aqueous solution of step (a) with the molten wax    solution of step (b) by mixing the two solutions in the presence of    a phase transfer catalyst;-   (d) separating the aqueous solution from the molten wax solution and    cooling the molten wax solution to a temperature at which the molten    wax solidifies to obtain the solid composition.

Preferably, in formula (VII) M is sodium; m is 2 and n is 1. It will beappreciated that compounds of formula (VII) may contain so-calledcrystal water. A preferred compound of formula (VII) is Na₂S.xH₂O.

The molar ratio of the compound of formula (VIII) to the compound offormula (VII) is preferably between 10:1 and 1:1, more preferablybetween 5:1 and 1.5:1, most preferably about 2:1.

In principle any phase transfer catalysts may be used. Examples ofpreferred phase transfer catalysts are quaternary ammonium orphosphonium salts. In view of the high costs of phosphonium salts, morepreferably the phase transfer catalyst is a tetra-alkyl ammonium salt,wherein at least one alkyl group is a C3-C20 alkyl group, morepreferably a C4-C12 group, even more preferably a C4 to C6 group.

Preferably, the counter ion in the quaternary ammonium or phosphoniumsalt is a monovalent ion, more preferably bromide. Good results havebeen obtained with tetra-butyl ammonium bromide; tetra-octyl ammoniumbromide; and cetyl tri-methyl ammonium bromide, in particulartetra-butyl ammonium bromide.

The temperature at which the reaction is carried out is preferably inthe range from 70 to 105° C., even more preferably 75 to 95° C.

The reaction is typically carried out in the liquid phase.

The reaction time typically varies with the temperature used, butgenerally will be in the range from 2 to 5 hours.

The solid composition is preferably supplied to step (a) in the form ofpellets. For the purpose of this specification, reference herein to“pellets” is to any type of regularly sized particle, for exampleflakes, slates or sphere-shaped units such as prills, granules, nuggetsand pastilles or half pea sized units.

The solid composition that is supplied to step (a) preferably comprisesat least 10 wt % of the coupling agent, based upon the weight of thesolid composition, more preferably at least 15 wt %, more preferably atleast 20 wt %, even more preferably at least 30 wt %. The solidcomposition preferably comprises less than 80 wt % of the couplingagent, based upon the weight of the solid composition, more preferablyless than 65 wt % and even more preferably less than 60 wt %, and evenmore preferably less than 50 wt %. Preferably the solid compositioncomprises from 20 to 60 wt % of the coupling agent, for example 30 to 60wt %, more preferably 20 to 50 wt %. It is desirable to maximise theamount of coupling agent in the composition as this is the agent thatimproves the properties of the sulphur cement product. However, if theamount of coupling agent is too high, it may not be possible to producea solid composition (many of the coupling agents are liquid) and thesolid composition may not be stable under the desired storage andtransport conditions.

The solid composition that is supplied to step (a) comprises at least 10wt %, based upon the weight of the solid composition, of carriermaterial selected from one or more of wax, inorganic filler and polymer.More preferably the solid composition comprises at least 40 wt % ofcarrier material and most preferably the solid composition comprises atleast 50 wt % of carrier material. Preferably the solid compositioncomprises from 50 to 80 wt % of the carrier material. The amount ofcarrier material must be sufficient to achieve a solid and stablecomposition.

The solid composition may comprise further components in addition to thecoupling agent and the carrier material, but preferably the couplingagent and the carrier material provide at least 80 wt % of the solidcomposition, more preferably at least 90 wt % of the solid composition.In a preferred embodiment, the solid composition consists essentially ofthe coupling agent and the carrier material. The solid compositionpreferably comprises less than 5 wt % elemental sulphur, and preferablydoes not comprise elemental sulphur.

The carrier material is selected from one or more of wax, inorganicfiller and polymer. Preferably, the carrier material comprises wax. Morepreferably the carrier material comprises wax and an inorganic filler.

The wax is preferably a paraffin wax, such as a paraffin wax resultingfrom a Fischer-Tropsch process. Fischer-Tropsch waxes are known to thoseskilled in the art. A detailed account of Fischer-Tropsch waxes waspublished as “Fischer-Tropsch Waxes”, ISBN 0620075600, on 13 Mar. 1984,ed. J H Le Roux and S Oranje; published by Sasol One (PTY) Ltd andSasolChem (PTY Ltd), Republic of South Africa. Fischer-Tropsch waxes areavailable commercially from Sasol and Shell MDS (Malaysia) Shd Bhd. Thelatter products have for example been described in “The Markets forShell Middle Distillate Synthesis Products”, presentation by Peter Tijm,Shell International Gas Ltd., Alternative Energy '95, Vancouver, Canada,May 2-4, 1995.

Typically, the Fischer-Tropsch waxes have been hydrogenated and/orhydrofinished to remove or substantially reduce any olefins oroxygenates formed in the Fischer-Tropsch reaction. A preferredFischer-Tropsch synthesis process is disclosed in WO-A-9934917. Thesynthesis product as directly obtained in the Fischer-Tropsch process ispreferably hydrogenated in order to remove any oxygenates and saturateany olefinic compounds present in such a product. Such a hydrotreatmentis described in for example EP-B-0668342. A preferred process forpreparing Fischer-Tropsch waxes is disclosed in U.S. Pat. No. 5,486,542.

Preferably, the paraffin wax comprises at least 80% mol, more preferablyat least 85% mol., even more preferably at least 90mol % of straightchain alkanes, as determined using a ¹³C NMR. This method determines anaverage molecular weight for the wax and subsequently determines the molpercentage of molecules having an methyl branch, the mol percentage ofmolecules having an ethyl branch, the mol percentage of molecules havinga C₃ branch and the mol percentage having a C₄ ⁺ branch, under theassumption that each molecule does not have more than one branch. Themol% of branched alkanes is the total of these individual percentages.Preferably the alkane chain length is in the range from about C30 toabout C100 or even higher.

Preferably, the congealing point (ASTM D938) of the wax is from 60 to130° C., more preferably from 70 to 120° C., even more preferably 70 to110° C. Even more preferably, the congealing point of the wax used isfrom 70 to 95° C., especially if the coupling agent is produced byreacting by mixing an aqueous solution of an oligosulphide with acompound of formula (VIII) in a hydrophobic molten wax phase in thepresence of a phase transfer catalyst.

Preferably, the wax has an oil content (ASTM D721) of less than 5% wt,more preferably less than 2% wt, even more preferably less than 1% wt.

The wax may also be a refined slack wax. Slack wax is a crude waxproduced by chilling and solvent filter-pressing wax distillate inrefinery operations. A refined slack wax is a slack wax that has beensubjected to a hydrotreating operation prior to or after separation fromthe wax containing distillate.

According to another preferred embodiment, the wax is a microcrystallinewax. Microcrystalline waxes are known in the art and availablecommercially. It has been found that microcrystalline wax isparticularly preferred if it is desired not to use inorganic filler inthe solid composition as the presence of microcrystalline wax results ina particularly stable solid composition.

According to a particularly preferred embodiment, the solid compositioncomprises an inorganic filler and a blend of 10 to 90% wt ofFischer-Tropsch wax containing at least 80% mol straight chain alkanesand 90 to 10% wt. of a microcrystalline wax, based on the total amountof wax present.

Preferably the carrier material comprises from 25 to 75wt % wax, basedupon the weight of the carrier material.

The inorganic filler is preferably chosen from one or more of carbonblack, metal carbonates (e.g. calcium carbonate), silica, titania, ironoxide, alumina, asbestos, fly ash, limestone, quartz, gypsum, talc,mica, metal silicates (e.g. calcium silicate) or powdered elementalsulphur. Most preferably the inorganic filler is carbon black, silica,calcium carbonate or calcium silicate. The average particle size of theinorganic filler is preferably in the range of from 0.1 μm to 0.1 mm.Preferably the carrier material comprises from 25 to 75wt % of inorganicfiller, based upon the weight of the carrier material.

The carrier material may comprise polymer such as polyethylene or anethylene copolymer (e.g. ethylene vinyl acetate).

The present invention further provides a solid composition particularlysuitable for use in the process of the present invention. The solidcomposition comprises from 20 to 70 wt % of a coupling agent chosen fromthe group of organosilanes and organotitanates, from 20 to 60 wt % ofwax or polymer, and from 10 to 50 wt % of inorganic filler, wherein theweight percentages are based upon the weight of the solid composition.Preferably the solid composition comprises from 20 to 70 wt % of acoupling agent chosen from the group of organosilanes andorganotitanates, from 20 to 60 wt % of wax, and from 10 to 50 wt % ofinorganic filler. The preferred organosilanes and organotitanates, waxesand inorganic filler are as outlined above for the process of theinvention. Most preferably the solid composition comprises from 20 to 70wt % coupling agent, from 20 to 60 wt % wax and from 15 to 30 wt %inorganic filler.

In a preferred embodiment of the process of the invention, the sulphuris supplied in the form of pellets and the solid composition comprisingthe coupling agent is supplied in the form of pellets. Therefore, thepresent invention further provides a mixture of sulphur pellets andsolid composition pellets, wherein the solid composition comprises acoupling agent chosen from the group of organosilanes andorganotitanates, and at least 10 wt %, based upon the weight of thesolid composition, of carrier material selected from one or more of wax,inorganic filler and polymer. This mixture of sulphur pellets and solidcomposition pellets can be provided to step (a) of the process of theinvention such that sulphur and coupling agent are mixed withparticulate inorganic material at a temperature at which sulphur ismolten. The preferred weight ratio of sulphur pellets to solidcomposition pellets is from 997:3 to 97:3, preferably from 995:5 to985:15. Most preferably the solid composition pellets comprise from 20to 70 wt % coupling agent, from 20 to 60 wt % wax and from 10 to 50 wt %inorganic filler.

In another embodiment of the invention the coupling agent is two or moredifferent coupling agents, e.g. an organosilane and an organotitanate,or two different organosilanes, and the different coupling agents aresupplied as different solid compositions.

The sulphur cement product produced by the process, of the presentinvention is suitable for use in typical sulphur cement productapplications. A sulphur cement produced by the process can be combinedwith aggregate to provide a sulphur-cement aggregate composite. Sulphurconcrete produced by the process of the present invention can be mouldedto provide products such as paving materials and sea defences.

EXAMPLES

The invention is further illustrated by means of the followingnon-limiting examples.

Preparation of Pellets Comprising Coupling Agent

The coupling agent used in all examples wasbis(3-triethyoxysilylpropyl)tetrasulphide (TESPT). Pellets were preparedby hot-blending the TESPT, wax and inorganic filler. The inorganicfiller was first mixed with the TESPT, then wax was added. Heat wasapplied such that the wax melted and a homogeneous suspension wasobtained. The suspension was then poured onto a thin tray, allowed tocool, then broken mechanically into small (1-2 cm width, 2-4 mmthickness) chunks.

The pellet formulations are given in table 1. Wax type 1 is a FischerTropsch paraffin wax with a congealing point in the range of 95-105° C.Wax type 2 is a Fischer Tropsch paraffin wax with a congealing point inthe range of 100-110° C. The carbon black was N115 carbon black fromEvonik. The calcium carbonate is Wigro calcium carbonate. The titaniawas P25 titania from Evonik.

TABLE 1 TESPT Wax Inorganic filler Example 1 47 wt % Type 1 Carbon black35 wt % 18 wt % Example 2 35 wt % Type 1 Carbon black 52 wt % 13 wt %Example 3 25 wt % Type 2 Carbon black 50 wt % 25 wt % Example 4 60 wt %Type 2 Titania 20 wt % 20 wt % Example 5 55 wt % Type 2 Carbon black 28wt % 17 wt % Example 6 24 wt % Type 2 Calcium carbonate 28 wt % 48 wt %Example 7 31 wt % Type 2 Calcium carbonate 38 wt % 31 wt %

Aging of Pellets

The pellets were aged by treating under water for 7 days at 70° C.Successful resistance to aging was measured on the basis of a number ofcriteria: turbidity of water (none); release of H₂S or SO₂ into theaging vessel headspace (none); change in appearance or consistency ofthe pellets (none); performance of the mortar prepared with the agedpellets with respect to water intrusion and flexural strength, whencompared to both the non-aged pellets and a mortar of identicalcomposition but not using a pre-pelletisation step.

Preparation of Sulphur Mortars

Mortars were prepared using fresh pellets, aged pellets and also using anon-pellet approach wherein all the components (TESPT, wax, inorganicfiller) were used in the same amounts but not in the form of a pellet.For each mortar the amount of TESPT was standardised to 0.06 wt %, basedupon the weight of the sulphur mortar.

Two different methods were used to prepare sulphur mortars:

-   Method A: Sand (56.3 wt %) and filler (fly ash, 19.0 wt %) were    pre-heated in an oven at 150° C. while sulphur was pre-heated at    65° C. The sand was transferred to an oil-heated steel bowl (the    temperature of the bowl was 150° C.). The pellets (or in case of no    pellets the ingredients separately) were added. After three to five    minutes sulphur was added to the sand and pellets and mixed until    homogeneous. The mixture was then stirred and heated until the    sulphur was molten. The fly-ash was subsequently added to the mix.    This mixture was then stirred until uniform. The mixture was    transferred into three pre-heated silicon moulds and cooled down to    room temperature before demoulding.-   Method B: 1057.5 g of preheated sand and pellets (or in case of no    pellets the ingredients separately) were mixed. 560.07 g of    preheated sulphur was subsequently added. 630 g of preheated quartz    was added and mixed for 5 minutes after homogenisation. The molten    product was transferred into preheated silicon moulds, thereby    producing three sulphur mortar prisms after cooling.

Properties of Sulphur Mortars

The water intrusion after 14 days, expressed as a weight percentage, ofthe mortar samples was measured and is given in table 2. The flexuralstrength before and after water aging of the sulphur mortar was measuredby a three point bending test (using Toni Technik apparatus) and theresults are given in Table 2.

TABLE 2 Water intrusion after Flexural strength before/after Aging of 14days (%) water aging (N/mm²) Pellet pellet Non-aged Aged Non-aged AgedComposition Pass/Fail No pellet pellet pellet No pellet pellet pelletExample 1 Pass 0.08 0.08 0.04 9.5/8.8 9.3/9.8 10.4/11.8 Example 2 Pass —0.08 0.05 — 9.0/7.7 9.7/9.5 Example 3 Pass 0.05 0.07 0.08 12.2/12.29.7/9.4 10.4/8.6  Example 4 Pass 0.08 0.10 0.46  9.8/11.5 10.4/10.810.3/9.9  Example 5 Fail 0.04 0.07 0.4 12.0/12.6  9.7/10.3 9.6/9.9Example 6 Pass 0.15 — 0.06 11.3/9.9  — 11.1/9.7  Example 7 Pass — — 0.05— — 10.4/10.3

The sulphur mortars prepared from the fresh pellets had comparableproperties to those prepared using the no-pellet (separate ingredients)route. The water intrusion and flexural strength properties are notadversely affected by the inclusion of the carrier materials. Thesulphur mortars prepared from the aged pellets also show good waterintrusion and flexural strength properties, indicating the pellets arestable and can be used after having been stored.

The pellets of Example 4 passed the aging text but did not disassociatewhen incorporated into sulphur mortar. This means that the TESPTcoupling agent cannot be homogeneously dispersed throughout the sulphurmortar, as is desirable.

The pellets of Example 5 failed the aging test because the surface ofthe pellets had white spots and the water became turbid. The sulphurmortars prepared using the aged pellets of example 5 showed goodflexural strength but did not have the dark appearance of the mortarsprepared using the non-aged pellets and prepared without pellets.

Example 8 Preparation of a Solid Composition Comprising TESPT

In a roundbottom flask with a condenser and a magnetic stirrer, 1.92 g(0.06 mol) sulfur pellets (Shell), 2.60 g (0.02 mol) Na2S.xH2O 60%flakes (Aldrich), 2.0 g water, 0.10 g Tetrabutylammonium bromide(Aldrich), and 9.92 g paraffin wax mp 73-80 (Aldrich) were mixed andheated to 90° C. Once the solids had dissolved 9.94 g (0.04 mol)3-chloropropyltriethoxysilane was added (Aldrich). After 3 hours thestirrer was stopped upon which two layers with a sharp boundary formedrapidly: an upper layer of paraffin wax with silane and a bottom layerwith dissolved salts. The two layers were separated. NMR analysis showed90% conversion of the 3-chloropropyltriethoxysilane to TESPT and only 2%hydrolysis for the silane ethoxy groups.

Examples 9-21

The procedure of Example 8 was repeated but with variations of type andquantity of phase transfer catalyst (PTC), presence of a pH-buffer;amount of water and paraffinic wax; and variation in reactiontemperature. Results are depicted in Table 3.

TABLE 3 H2O Wax T C* Ex. PTC (g) Buffer (g) (g) (g) (° C.) (%) 9 TBAB0.20 — 0 2.0 10 100 90 10 TBAB 0.20 — 0 2.0 10 110 80 11 TBAB 0.20 — 010 12 100 80 12 TBAB 0.20 — 0 2.0 4.0 90 90 13 TBAB 0.20 — 0 2.0 2.7 9080 14 TBAB 0.21 NaHCO₃ 6.0 17 10 90 95 15 TBAB 0.21 NaHCO₃ 2.0 4.0 10 9099 16 TBAB 0.20 NaHCO₃ 1.0 5.0 10 90 97 17 TOAB 0.20 — 0 2.1 10 90 57 18TOAB 0.34 NaHCO₃ 6.0 19 10 90 50 19 CTAB 1.43 — 0 30 10 90 90 20 CTAB0.50 NaHCO₃ 7.1 19 10 90 80 21 CTAB 0.40 — 0 29 10 90 90 C* = conversionTBAB = tetrabutyl ammonium bromide TOAB = tetraoctyl ammonium bromideCTAB = cetyl trimethyl ammonium bromideAfter three hours it is expected that hydrolysis would be in the sameorder as obtained for Example 8.

1. A process for the preparation of a sulphur cement product comprisingthe steps of: (a) mixing sulphur with a coupling agent and with aparticulate inorganic material at a temperature at which sulphur ismolten to obtain a molten sulphur cement product; and (b) solidifyingthe molten sulphur cement product; wherein the coupling agent is chosenfrom the group of organosilanes and organotitanates, and wherein thecoupling agent is supplied as a solid composition comprising thecoupling agent and at least 10 wt %, based upon the weight of the solidcomposition, of carrier material selected from one or more of wax,inorganic filler and polymer.
 2. A process according to claim 1, whereinthe sulphur is supplied to step (a) in the form of sulphur pellets.
 3. Aprocess according to claim 1, wherein the coupling agent is anorganosilane having the general molecular formula (I):(P¹)₃Si-A-Si(P²)₃   (I) Wherein P¹ and P² are independently alkoxy,acyloxy, aryloxy, alkyl, aryl and halogen and A is a divalent functionalgroup comprising one or more groups chosen from thiol, sulphide, amineor alkenyl groups or an organosilane having the general molecularformula (III):(P³)₃Si-A′  (III) Wherein P¹ and P² are independently alkoxy, acyloxy,aryloxy, alkyl, aryl and halogen and A′ is an univalent functional groupcomprising one or more groups chosen from thiol, sulphide, amine oralkenyl groups.
 4. A process according to claim 1, wherein the couplingagent is an organosilane having the general molecular formula (II):(R¹O)₃Si-A-Si(OR²)₃   (II) wherein R¹ and R² are independently C₁₋₆alkyl and A is a divalent functional group comprising one or more groupschosen from thiol, sulphide, amine or alkenyl groups.
 5. A processaccording to claim 4, wherein A is a polysulphide group of formula—(CH₂)_(x)—S_(y)—(CH₂)_(z)— wherein x is an integer from 1 to 4, y is aninteger from 2 to 8, and z is an integer from 1 to
 4. 6. A processaccording to claim 1, wherein the coupling agent is an organosilanehaving the general molecular formula (I), and wherein the solidcomposition comprises wax as carrier material and the coupling agent isprepared by (a) providing an aqueous solution of an oligosulphide byreacting a compound of formula (VII):M_(m)S_(n)   (VII) wherein M is a nitrogen-containing cation, aphosphorus-containing cation or a metal atom, m is 1 or 2 and n is from1 to 8, or M is hydrogen, m is 2 and n is 1 with molten sulphur; (b)providing a compound of formula (VIII):

wherein R¹, R² and R³ are independently chosen from alkoxy, acyloxy,aryloxy, alkyl, aryl and halogen, preferably C1-C6 alkoxy, wherein R⁴ isalkylene and wherein X is a leaving group chosen from the groupconsisting of halogen, carboxylate, nitro, azide, thiocyanate, ammonium,phosphonium and sulfonate, dissolved in a molten hydrophobic wax; (c)reacting the aqueous solution of step (a) with the molten wax solutionof step (b) by mixing the two solutions in the presence of a phasetransfer catalyst; (d) separating the aqueous solution from the moltenwax solution and cooling the molten wax solution to a temperature atwhich the molten wax solidifies to obtain the solid composition.
 7. Aprocess according to claim 1, wherein the solid composition is suppliedto step (a) in the form of pellets.
 8. A process for preparing a solidcomposition for use in a process as claimed in claim 3 which comprises(a) providing an aqueous solution of an oligosulphide by reacting acompound of formula (VII):M_(m)S_(n)   (VII) wherein M is a nitrogen-containing cation, aphosphorus-containing cation or a metal atom, m is 1 or 2 and n is from1 to 8, or M is hydrogen, m is 2 and n is 1 with molten sulphur; (b)providing a compound of formula (VIII):

wherein R¹, R² and R³ are independently chosen from alkoxy, acyloxy,aryloxy, alkyl, aryl and halogen, preferably C1-C6 alkoxy, wherein R⁴ isalkylene and wherein X is a leaving group chosen from the groupconsisting of halogen, carboxylate, nitro, azide, thiocyanate, ammonium,phosphonium and sulfonate, dissolved in a molten hydrophobic wax; (c)reacting the aqueous solution of step (a) with the molten wax solutionof step (b) by mixing the two solutions in the presence of a phasetransfer catalyst; (d) separating the aqueous solution from the moltenwax solution and cooling the molten wax solution to a temperature atwhich the molten wax solidifies to obtain the solid composition.
 9. Asolid composition comprising from 20 to 70 wt % of a coupling agentchosen from the group of organosilanes and organotitanates, from 20 to60 wt % of wax or polymer, and from 10 to 50 wt % of inorganic filler,wherein the weight percentages are based upon the weight of the solidcomposition.
 10. A solid composition according to claim 9, comprisingfrom 20 to 50 wt % coupling agent, from 30 to 50 wt % wax and from 15 to30 wt % inorganic filler.
 11. A solid composition according to claim 9or claim 9, wherein the coupling agent is an organosilane having thegeneral molecular formula (II):(R¹O)₃Si-A-Si(OR²)₃   (II) wherein R¹ and R² are independently C₁₋₆alkyl, and A is a divalent functional group comprising one or moregroups chosen from thiol, sulphide, amine or alkenyl groups; wherein thewax is a paraffin wax having a melting point of from 70 to 120° C.; andthe inorganic filler is carbon black, calcium carbonate, calciumsilicate or titania.
 12. A mixture of sulphur pellets and solidcomposition pellets, wherein the solid composition comprises a couplingagent chosen from the group of organosilanes and organotitanates, and atleast 10 wt %, based upon the weight of the solid composition, ofcarrier material selected from one or more of wax, inorganic filler andpolymer.
 13. A mixture according to claim 12, wherein the solidcomposition pellets consist of a solid composition according to claim 9.